Integrative taxonomy of the Cercomacra cinerascens species complex with description of two new species (Aves: Thamnophilidae)

The genus Cercomacra includes six species, among them C. cinerascens, which is widespread throughout the Amazon Basin. Historically, six names have been proposed for this species complex, but only four are currently recognized. Past studies have explored relationships among Cercomacra species using either morphological or molecular data, with taxonomic assessments mainly conducted in the early 20 th century.

To reevaluate the validity of the currently accepted C. cinerascens taxa, we performed a comprehensive taxonomic revision that combined traditional morphological and vocal analyses. Additionally, we used BirdNET, a pre-trained deep learning algorithm developed for bird sound classification. We examined 682 specimens and 347 recordings and identified two distinct morphotypes distributed north and south of the Amazon Basin, along with four recognizable loudsong types.

Using both morphological and vocal features, we identified five distinct lineages, two of which are newly described and named. Cercomacra cinerascens occurs north of the Pastaza and Amazon Rivers in northern Amazonia; C. sclateri is found in eastern Ecuador and Peru, south of the Pastaza River and east of the Andes, east to the Ucayali River; and C. iterata stat. nov. is located east of the Tapajos River. The two newly described species are found south of the Amazon and Marañon Rivers.

Cercomacra mura sp. nov. occupies the Ucayali-Madeira interfluve, and Cercomacra raucisona sp. nov. inhabits the Madeira-Tapajos interfluve.